Fluid cooled lance

ABSTRACT

Fluid cooled lance formed of composite refractory and metal for conveying oxygen-containing or other gases, with or without entrained solids, into or onto molten baths, including a heat and corrosion-resistant nozzle in the lance adapted to provide a localized increase in the gas delivered from the lance. The lance also includes a plurality of individual small diameter pipes facilitating increased resistance to operating stresses, providing an increased cooling surface, and allowing for the reduction of its external refractory envelope.

United States Patent 1191 1111 3,751,019 Phillips 1 Aug. 7. 1973 1 FLUID COOLED LANCE 3,169,161 2/1965 Kurzinski 266/34 L 2,829,960 4/1958 Vogt [75] Inventor- James l P Mount, 3,201,104 8/1965 Berry 266/34 L Waverley, V1ctor1a, Australia OTHER PUBLICATIONS [73] Asslgnee' n of i i "s? German Printed Application: Rudolf Hebenstreit St 2 e 0 C 7695 Vl/l8a, 12/13/56. Australia [22] Filed: Nov. 16, 1971 Primary Examiner-Gerald A. Dost [21] pp No: 199,134 Attorney-Enc H. Waters et al.

[57] ABSTRACT Foreign Application Priority Dam Fluid cooled lance formed of composite refractory and Nov. 19, 1970 Australia 3251/70 metal for conveying oxygen-containing or other gases, with or without entrained solids, into or onto molten [52] US. Cl. 266/34 L baths, including a heat and corrosion-resistant nozzle in [5 1] Int. Cl. C2lc 5/32 the lance adapted to provide a localized increase in the [58] Field of Search 239/1323; 266/34 L, gas delivered from the lance. The lance also includes a 266/41 plurality of individual small diameter pipes facilitating increased resistance to operating stresses, providing an [56] References Cited increased cooling surface, and allowing for the reduc- UNITED STATES PATENTS tion of its external refractory envelope. 3,045,997 7/1962 Hudson 266/34 L 23 Claims, 3 Drawing Figures PAIENIEUAUG Hm FLUID COOLED LANCE This invention relates to improvements in cooled lances (which term in this specification is used to include pipes, nozzles, tuyeres and other tubular members used for conveying materials into vessels or furnaces used in pyrometallurgical and related industries) and the invention is concerned particularly with an improved disign of fluid cooled lance constructed of composite refractory and metal and as used in the metallurgical and chemical engineering industries for conveying oxygen-containing or other gases, with or without entrained solids, into or onto molten baths.

Conventional water-cooled lances suffer from certain short-comings, including:

a. Excessive removal of heat from the molten bath. Heat removed in this manner normally needs to be compensated for by an additional heat input thereby imposing an economic penalty.

b. Safety hazards due to the large volume of water submerged below, or in close proximity to, the molten bath.

c. Excessive build-ups at the tips of the lances due to freezing of constituents of the molten bath onto the lance itself. Such build-ups tend to cause blockages of the delivery outlets of the reaction gas and thereby disrupt the proper functioning of the lance. The burden of removal of theaccreted solids on occasions exceeds the capacity of the mechanical means available, for example, manual or pneumatic punches. Under these circumstances it is normal practice to replace the blocked lance with a new lance. This operation may cause disruption to the normal funtioning of the furnace or vessel in addition to the cost of the replacement lance. Alternatively the use of high gas pressures to reduce blockages increases the cost of the equipment and power required to compress the gas to appropriate pressures of, say, 50 to 80 p.s.i.g.

. d; Damage to the metal components of the lance by molten bath constituents or hot gases arising from an inability to maintain consistently a protective layer of refractory or solidified bath material between the metal components and the molten bath.

Refractory-clad metal lances (composite lances) which are not liquid cooled are known to be subject to progressive failure commencing from the tip (particularly when jetting oxygen-rich gases) or to localised failure along the submerged length or at the surface of the molten bath, or toa combination of any of these.

The present invention seeks to overcome these difficulties by a composite metal and refractory lance which in its preferred form has the following features:

a. provision of adequate lance cooling by means of relatively low volumes of cooling liquid,

b. low rate of heat extraction from the molten bath,

c. when used in conjunction with commercially available mechanical punching apparatus, the ability to convey reaction gases at moderate supply pressures, for example less than 25 p.s.i.g., into a molten bath without blockage of the gas outlet occurring,

d. rugged construction to withstand thermal and mechanical stresses caused by movements ofthe lance and by the removal of accreted solids from the tip.of the lance by punching during extended periods of continuous operation.

Lances constructed and operated in accordance with this invention have demonstrated the ability to operate continuously for extended periods in environments of high temperature and/or in molten baths in furnaces or vessels, as used in the pyrometallurgical and related industries. For example, when used for injecting air into a molten bath of copper matteand slag at a temperature of about 1250 C for the purpose of oxidising its iron and sulphur contents to produce blister copper, such lances have operated continuously for periods in excess of 2 weeks providing typical air flows of 600 N.C.f.m. from a supply at 18 to 20 p.s.i.g. pressure and extracting heat at a typical rate of 140,000 B.T.U. per hour. The cooled lance of this invention is preferably used with gas supply pressures not greater than 25 p.s.r.g.

An important feature of the invention is the provision of a nozzle connected to and communicating with the central metal tubular member of the liquid cooled lance, the nozzle being formed of heat resistant material and preferably being of smaller diameter than the central tubular member. The material of which the nozzle extension is formed is preferably capable of substantially resisting corrosion, erosion or other damage at temperatures in excess of 600 (C, for example, when the lance is used for injecting oxy'gen containing gases into baths of molten metals or mattes. A suitable heat resistant material of which the nozzle may be constructed is the material marketed under the registered trade mark Cobalide 23 (also known as UM Co 50).

The nozzle is preferably of smaller diameter than the central metal tubular member in order to achievea localised increase in the velocityof the gasdelivered from the lance.

Preferably the nozzle extends for a sufficient distance from the cooled face ofthe centrall metal tubular member to substantially prevent the'cooled section of the lance coming into contact with the region of greatest bath turbulence. As a result, the end of the nozzle remote from the cooled face of the central tubular member is caused to operate at higher temperatures than the remainder of the metal components of the lance. Accretion of solidified bath material around the point of delivery of reaction gas from the lance into or onto the molten bath is thus appreciably less and the likelihood of lance blockages is substantially reduced.

Another feature of the invention is the use of a plurality of individual pipes of relatively small diameter to carry the cooling medium rather than having two concentric pipes of large diameter forming an annular passage for the coolant. This results in the following advantages:

a. Failure of a single pipe results in only limited ingress of cooling liuqid into the furnace, a significantadvantage from a safety point of view.

b. The multiplicity of cooling pipes provides an an- .chor which materially assists the refractory enevelope to remain intact under the action of thermal and mechanical stresses.

c. The surface area of cooling pipes exposed to a hot face for a desired degree of cooling is minimal.

d. The external diameter of the refractory envelope required is effectively reduced.

The invention comprises a central metal tubular member through which the reaction gases pass into or onto the molten bath. The central tube also functions as the principal structural member of the lance and therefore is constructed of material of sufficient mechanical strength and in sufficient sectional thickness to prevent undue flexing or bending of the lance in operation.

Around the periphery of the central pipe are arranged cooling pipes of smaller diameter made from metal or alloy of suitable strength and thermal conductivity. For example, low carbon or mild steel has been found to have a suitable combination of strength and thermal conductivity and has the added attraction of low cost and ready availability. The outside diameter of the cooling pipes may range upwards from one-eighth inch,preferably greater than one-fourth inch, and is preferably less than one-quarter of the outside diameter of the central lance pipe around which the cooling pipes are positioned.

The spacing between the cooling pipes should preferably be upwards from one-eighth inch depending on the nature of the refractory material to be moulded around the tube assembly. The cooling tubes are separated sufticiently to permit the refractory material to fill the spaces between them and to achieve good contact with the cooling pipes. Anchoring of the refractory material against radial forces tending to remove it is thereby achieved. Optimum spacing depends largely on the particle size distribution of the refractory, its moulding characteristics and its thermal conductivity.

The cooling pipes may be arranged in linear, parallel, spiral or curved configurations, or combination of any of these, or in any other desired configuration consistent with the nature and objectives of particular conditions, for example:

a. several cooling tubes extending along the sides of the main lance pipe, parallel to each other and to the axis of the main lance pipe to provide cooling of uniform intensity along the length of the lance,

b. several cooling tubes wound spirally at varying pitches around the periphery of the main lance pipe to provide cooling of the varying intensity along the length of the lance.

The cooling tubes are preferably attached to the lance only at or near to the lance tip. Freedom of movement of the cooling pipes relative to the main lance member is thus provided, such movement being caused by thermal expansion and contraction and by the flexing of the lance in operation.

The cooling tubes are preferably connected to a supply and exhaust system which ensures uniform distribution of the cooling liquid between the individual tubes, for example, ring manifolds of suitable diameter.

The velocity of the cooling liquid in the cooling tube is such as to provide capacity for high rates of heat transfer across the metal/liquid interface. An average velocity of at least feet per second is considered desirable and preferably an average velocity of 25 feet per second should be attained. By this means a high heat flux across the liquid metal/refractory coating/cooling tube system can be tolerated without, in the case of water cooling for example, causing vapour blanket boiling and excessive temperatures in the cooling tube wall.

In another important aspect of the invention, cooling liquid in the aforementioned cooling pipes is delivered to and exhausted from an annular cooling channel contained within a metallic tip ring at or near the lance tip. The pipes are preferably so arranged that a delivery pipe and exhaust pipe are positioned alternately around the tip ring. In this manner continous uniform cooling in a transverse plane is achieved. The dimensions and configuration of the cooling channel are such as to provide capacity for high rates of heat transfer across the metal liquid interface by inducing turbulence of the cooling liquid. The metallic tip ring is thereby stabilised against the effects of high environmental temperature and possible contact with the molten bath. The tip ring also serves to protect the cooling tubes and the surrounding refractory in the region of the lance tip. The tip ring may be constructed of any suitable material such as, for example, stainless steel, mild steel, copper and copper alloys.

The reaction gases are delivered from the main lance pipe into or onto the molten bath via the nozzle which preferably extends in the desired direction from the cooled face of the lance tip ring.

A refractory material, such as, for example, one based on alumina, magnesite or chromite, and preferably also including a suitable reinforcement, is preferably moulded around the main lance pipe, the nozzle, the cooling tubes and other components, where these elements are liable to be exposed to conditions of high temperature. The thickness of the refractory is preferably between one-fourth inch and 4 inches. The reinforcement, for example, metal mesh or expanded and spirally wound spring, increases the mechanical strength of the refractory and its resistance to spalling.

The cooling medium employed in the cooling tubes and other cooled components may be water, oil or any other suitable liquid.

Reference will now be made to the preferred form of the invention shown in the accompanying drawings, wherein:

FIG. 1 is a diagrammatic view in elevation of one form of water cooled lance constructed in accordance with the invention.

FIG. 2 is a diagrammatic and partially sectional view of the delivery end of the lance shown in FIG. 1.

FIG. 3 is a diagrammatic sectional view of the portion of the lance shown in FIG. 2.

Identical reference numerals have the same connotations on all drawings.

The lance comprises a central metal lance pipe 10 which delivers reaction gases or gaseous entrained solids from a supply system (not shown) into or onto a molten bath (not shown) via an extension nozzle 11. The end 12 of the cental lance pipe 10 tapers towards the nozzle 11 which is preferably of smaller diameter than the main lance pipe 10.

The nozzle 11 is formed of heat resistant material which is capable of substantially resisting corrosion, erosion or other damage by the materials of the molten bath, at temperatures in excess of 800 C and preferably temperatures of the order of l,250 C.

The cross-sectional area of the interior of the central lance pipe 10 is preferably two to four times the crosssectional area of the interior of the nozzle 11.

The central lance pipe 10 is surrounded by a plurality of cooling pipes 14 spaced at uniform intervals around its periphery and in close proximity to its external surface. The cooling pipes 14 extend longitudinally of the lance pipe 10 and are of small diameter relative to that of the lance pipe 10.

The cooling tubes 14 deliver to and exhaust the cooling liquid from an annular channel 15 contained within a metallic tip ring 16 which is suitably joined to the central lance pipe 10 and/or the nozzle extension 11. The tip ring 16 surrounds the end of the nozzle 11 which abuts against the end of the lance pipe 10. Each cooling pipe 14 is attached and sealed to the ring 16 to prevent loss of cooling liquid. The tubes 14 are preferably not integrally secured to the central pipe except possibly by a form of strapping (not shown) which may assist assembly of the lance. Relative movement of the cooling pipes 14 and the central pipe 10 is thereby assured to allow for possible thermal expansion or flexing in operation. The cooling pipes 14 are supplied with cooling liquid from an inlet manifold 18 and exhaust cooling liquid from an outlet manifold 19, which manifolds ensure an even distribution of the cooling liquid.

The pipes 14 are so arranged that a supply pipe and an exhaust pipe are positioned alternately around the lance pipe 10 and ring 16, so as to ensure uniform cooling in a transverse plane.

A refractory envelope 20 surrounds the central pipe 10, cooling pipes 14 and preferably also the tip ring 16 and extension nozzle 11. The refractory envelope 20 preferably also incorporates an embedded reinforcement made of, for example, metal mesh or expanded spirally wound wire (not shown). Metal anchors (not shown), e.g. of Y shape, may be used to assist in affixing the refractory envelope 20 in position.

In this specification the following abbreviations have the following meaning:

p.s.i.g. pounds (avoirdupois) per square inch gauge N.C.f.m. Normal cubic feet per minute B.T.U. British Thermal Units.

I claim:

l. A fluid cooled lance comprising a central metal tubular member, and a nozzle connected to and communicating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material, the central metal tubular member being cooled by a series of cooling tubes of small diameter relative to that of the central tubular member, said cooling tubes being arranged to surround the central tubular member and to extend longitudinally thereof, said cooling tubes being connected to a supply ofcool ing medium or to exhaust, the supply pipes and exhaust pipes being arranged alternately around the lance.

2. A fluid cooled lance according to claim 1 wherein the material of which the nozzle is formed is resistant to corrosion or other damage by molten bath materials at temperatures in excess of 600 C.

3. A fluid cooled lance according to claim 1 wherein the diameter of the nozzle is smaller than that of the central metal tubular member.

4. A fluid cooled lance according to claim 1 wherein the cross-sectional area of the interior of the central metal tubular member is from two to four times the cross-sectional area of the interior of the nozzle.

5. A fluid cooled lance according to claim 1 wherein the external diameter of each cooling tube or pipe is not greater than one-quarter of the external diameter of the central tubular member.

6. A fluid cooled lance according to claim 1 wherein the cooling tubes or pipes are connected to an annular channel formed in a tip ring which surrounds the nozzle and the end of the central tubular member adjacent thereto.

7. A fluid cooled lance according to claim 1 wherein the outlet end of the central tubular member is tapered inwardly to meet the adjacent end of the nozzle.

8. A fluid cooled lance according to claim 1 wherein the central tubular member is surrounded by an envelope of refractory material, in which the cooling tubes and the nozzle are embedded.

9. A fluid cooled lance according to claim 1 wherein the cooling tubes or pipes extend parallel to the central tubular member.

10. A fluid cooled lance according to claim 1 wherein the cooling tubes or pipes extend helically around the central tubular member.

11. A fluid cooled lance according to claim 1 and connected to a supply of reaction gas at a pressure less than p.s.i.g.

12. A fluid cooled lance comprising a central metal tubular member, and a nozzle connected to and communicating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material, the central metal tubular member being cooled by a series of cooling tubes of small diameter relative to that of the central tubular member, said cooling tubes being arranged to surround the central tubular member and to extend longitudinally thereof,

' said cooling tubes being connected to a supply of cooling medium or to exhaust, the supply pipes and exhaust pipes being arranged alternately around the lance, the supply pipes being connected to a supply manifold and the exhaust pipes being connected to an exhaust manifold, said manifolds being arranged to surround the central tubular member and being; located at the ends of said pipes remote from the tip ring.

13. A fluid cooled lance comprising a central metal tubular member, and a nozzle connected to and communicating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material, the central metal tubular member being cooled by a series of cooling tubes of small diameter relative to that of the central tubular member, said cooling tubes being arranged to surround the central tubular member and to extend longitudinally thereof, said cooling tubes being not secured to the central tubular member except near the outlet end thereof.

14. A fluid cooled lance comprising a central metal tubular member, a nozzle connected to and communieating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material which is substantially resistant to 'corrosion and damage by molten bath materials at temperatures in excess of 600 C, said'nozzle being of smaller diameter than the central metal tubular member, a plurality of cooling pipes extending longitudinally of and surrounding the central metal tubular member, said cooling pipes being of small diameter relative to that of the central metal tubular member, and a refractory envelope surrounding said central metal tubular member and said nozzle and in which said cooling pipes are embedded.

15. A fluid cooled lance according to claim 14 wherein the cross-sectional area of the interior of said central metal tubular member is from two to four times the cross-sectional area of the interior of said nozzle.

16. A fluid cooled lance according to claim 14 wherein the external diameter of each cooling pipe is not greater than one-quarter of the external diameter of said central metal tubular member.

17. A fluid cooled lance according to claim 14 wherein said cooling pipes are connected to an annular channel formed in a tip ring surrounding said nozzle.

18. A fluid cooled lance according to claim 14 wherein some of said cooling pipes are connected to a supply of cooling medium and the remainder of said cooling pipes are connected to exhaust, the supply pipes and exhaust pipes being arranged alternately around the lance.

l9. A fluid cooled lance according to claim 18 wherein said supply pipes are connected to a supply manifold and the exhaust pipes are connected to an exhaust manifold, said manifolds being arranged to surround the central metal tubular member near its inlet end.

20. A fluid cooled lance according to claim 14 wherein the outlet end of the central metal tubular member is tapered inwardly to meet the adjacent end of the nozzle.

21. A fluid cooled lance according to claim 14 wherein said cooling pipes extend parallel to the cen' thereof. 

2. A fluid cooled lance according to claim 1 wherein the material of which the nozzle is formed is resistant to corrosion or other damage by molten bath materials at temperatures in excess of 600* C.
 3. A fluid cooled lance according to claim 1 wherein the diameter of the nozzle is smaller than that of the central metal tubular member.
 4. A fluid cooled lance according to claim 1 wherein the cross-sectional area of the interior of the central metal tubular member is from two to four times the cross-sectional area of the interior of the nozzle.
 5. A fluid cooled lance according to claim 1 wherein the external diameter of each cooling tube or pipe is not greater than one-quarter of the external diameter of the central tubular member.
 6. A fluid cooled lance according to claim 1 wherein the cooling tubes or pipes are connected to an annular channel formed in a tip ring which surrounds the nozzle and the end of the central tubular member adjacent thereto.
 7. A fluid cooled lance according to claim 1 wherein the outlet end of the central tubular member is tapered inwardly to meet the adjacent end of the nozzle.
 8. A fluid cooled lance according to claim 1 wherein the central tubular member is surrounded by an envelope of refractory material, in which the cooling tubes and the nozzle are embedded.
 9. A fluid cooled lance according to claim 1 wherein the cooling tubes or pipes extend parallel to the central tubular member.
 10. A fluid cooled lance according to claim 1 wherein the cooling tubes or pipes extend helically around the central tubular member.
 11. A fluid cooled lance according to claim 1 and connected to a supply of reaction gas at a pressure less than 25 p.s.i.g.
 12. A fluid cooled lance comprising a central metal tubular member, and a nozzle connected to and communicating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material, the central metal tubular member being cooled by a series of cooling tubes of small diameter relative to that of the central tubular member, said cooling tubes being arranged to surround the central tubular member and to extend longitudinally thereof, said cooling tubes being connected to a supply of cooling medium or to exhaust, the supply pipes and exhaust pipes being arranged alternately around the lance, the supply pipes being connected to a supply manifold and the exhaust pipes being connected to an exhaust manifold, said manifolds being arranged to surround the central tubular member and being located at the ends of said pipes remote from the tip ring.
 13. A fluid cooled lance comprising a central metal tubular member, and a nozzle connected to and communicating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material, the central metal tubular member being cooled by a series of cooling tubes of small diameter relative to that of the central tubular member, said cooling tubes being arranged to suRround the central tubular member and to extend longitudinally thereof, said cooling tubes being not secured to the central tubular member except near the outlet end thereof.
 14. A fluid cooled lance comprising a central metal tubular member, a nozzle connected to and communicating with the central metal tubular member at its outlet end, the nozzle being formed of heat resistant material which is substantially resistant to corrosion and damage by molten bath materials at temperatures in excess of 600* C, said nozzle being of smaller diameter than the central metal tubular member, a plurality of cooling pipes extending longitudinally of and surrounding the central metal tubular member, said cooling pipes being of small diameter relative to that of the central metal tubular member, and a refractory envelope surrounding said central metal tubular member and said nozzle and in which said cooling pipes are embedded.
 15. A fluid cooled lance according to claim 14 wherein the cross-sectional area of the interior of said central metal tubular member is from two to four times the cross-sectional area of the interior of said nozzle.
 16. A fluid cooled lance according to claim 14 wherein the external diameter of each cooling pipe is not greater than one-quarter of the external diameter of said central metal tubular member.
 17. A fluid cooled lance according to claim 14 wherein said cooling pipes are connected to an annular channel formed in a tip ring surrounding said nozzle.
 18. A fluid cooled lance according to claim 14 wherein some of said cooling pipes are connected to a supply of cooling medium and the remainder of said cooling pipes are connected to exhaust, the supply pipes and exhaust pipes being arranged alternately around the lance.
 19. A fluid cooled lance according to claim 18 wherein said supply pipes are connected to a supply manifold and the exhaust pipes are connected to an exhaust manifold, said manifolds being arranged to surround the central metal tubular member near its inlet end.
 20. A fluid cooled lance according to claim 14 wherein the outlet end of the central metal tubular member is tapered inwardly to meet the adjacent end of the nozzle.
 21. A fluid cooled lance according to claim 14 wherein said cooling pipes extend parallel to the central metal tubular member.
 22. A fluid cooled lance according to claim 14 wherein said cooling pipes extend helically around the central metal tubular member.
 23. A fluid cooled lance according to claim 14 wherein said cooling pipes are not secured to the central metal tubular member except near the outlet end thereof. 